The present invention relates most generally to semiconductor devices and methods for manufacturing the same. More particularly, the present invention provides a method and structure for preventing base groups from becoming nested in low-k dielectric materials and subsequently rendering photoresists insoluble.
Deep ultra-violet (DUV) lithography is widely used in the fabrication of advanced VLSI (Very Large Scale Integration) semiconductor devices. Chemically amplified DUV photoresists improve the performance of the lithography systems and improve device feature resolution. Low dielectric constant (low-k) dielectrics are favored in today""s semiconductor manufacturing industry because of the performance improvements they provide by way of reducing parasitic capacitance, reducing propagation delay and therefore increasing device speed. The use of copper interconnect features is also favored to reduce line resistance of the interconnect lines. Typical copper interconnect schemes incorporate damascene manufacturing techniques to define the interconnect paths. A dual damascene approach is favored because it provides lower cost processing, improved level-to-level alignment tolerance and thus allows for tighter design rules and improved performance.
A shortcoming associated with the use of low-k dielectrics in conjunction with copper interconnect lines and chemically amplified photoresists used in DUV lithography, is that base groups which become nested in porous low-k dielectric materials, can interact with the acid catalysts included in chemically amplified photoresists to render the exposed photoresist insoluble in developer. This unwanted residual photoresist distorts the pattern being formed and is difficult to remove. Base groups such as amines or other Nxe2x80x94H base groups, are typically produced in association with conventional hard mask films, etch stop layers and barrier films used in the film stack that also includes the low-k dielectric films, and which is advantageously used in dual damascene processing. Etch stop layers and barrier films are commonly nitrogen-containing films.
It is therefore desirable to enjoy the benefits provided by copper interconnect technology, low-k dielectric films and chemically amplified photoresists in DUV lithography systems, without degrading the chemically amplified photoresist by interaction with base groups from low-k dielectric films.
The present invention provides a method and structure for isolating low-k dielectric layers from nitrogen base layers that include Nxe2x80x94H base groups which are capable of diffusing from the nitrogen base layer and becoming nested in the low-k dielectric layer. The present invention provides an oxygen-containing layer disposed directly between the low-k dielectric layer and the nitrogen base layer.
The present invention also provides a process for forming a semiconductor product which includes forming at least one low-k dielectric film over a substrate, forming at least one Nxe2x80x94H base film over the substrate using a source chemistry which includes ammonia, and forming a TEOS (tetraethyl orthosilicate) oxide film between at least one adjacent set of a low-k dielectric film and an Nxe2x80x94H base film.